The present invention relates generally to gas turbine engines. More particularly, the present invention relates to a diffuser for disposition between the compressor and combustor of a gas turbine engine. Although the present invention was developed for use in a gas turbine engine, certain applications of the invention may fall outside of this field.
A gas turbine engine is typical of the type of turbo machinery in which the present invention may be advantageously employed. It is well known that a gas turbine engine conventionally comprises a compressor for compressing a fluid, such as air, to an increased pressure. In a typical gas turbine engine, increased pressure fluid from the compressor is passed through a diffuser which conditions the fluid for subsequent combustion in the combustor.
The conditioned fluid is intermixed with fuel, ignited and burned in the combustor to generate a high temperature, relatively low pressure gaseous flow stream. The gaseous flow stream flows through a combustion chamber, where it is discharged and directed by a series of turbine vanes to a series of turbine blades. The turbine blades convert the thermal energy from the high temperature gaseous flow stream into rotational kinetic energy, which in turn is utilized to develop shaft power to drive mechanical components such as the compressor, fan, propeller, output shaft or other such devices. Alternatively, the high temperature gaseous flow stream may be used directly as a thrust for providing motive force, such as in a turbine jet engine.
Many prior diffusers include rigidly connected inner and outer walls that are typically formed as single-piece castings. Loads are transferred between the inner and outer walls through a series of struts formed integral therewith and disposed within the diffuser flowpath. Because of differing rates of thermal expansion between the inner and outer walls, significant thermal stresses are developed within the struts and at the point of connection between the struts and the inner and outer walls during operation of the engine. One approach to minimize the thermal stresses is to increase the width of the struts. Wider struts respond slower to thermal transients, thereby minimizing gradients across the strut, and are capable of carrying larger loads than thinner struts. However, increasing strut width correspondingly increases flow blockage in the diffuser flowpath, which may lead to increased disruption in air flow and a corresponding reduction in engine efficiency.
The profile tolerance and surface finish of the aerodynamic flowpath defined by the inner and outer diffuser walls in a cast single-piece diffuser is often not satisfactory to meet the design parameters for conditioning the compressed air exiting the compressor. The inconsistencies in profile tolerance result in unsatisfactory pressure changes and the surface finish in many single-piece diffusers creates aerodynamic drag which has the effect of reducing engine efficiency. A technique sometimes used to improve the profile tolerance and surface finish of the aerodynamic flowpath is to machine the interior surfaces of the diffuser. However, such machining is difficult due to the nature of single-piece castings, and also has the effect of greatly increasing the cost of the diffuser.
Thus, a need remains for further contributions in the area of diffuser technology. The present invention satisfies this need in a novel and non-obvious way.
One form of the present invention contemplates a diffuser for a gas turbine engine having first and second structures and a member coupled therebetween to maintain the first and second structures in spaced relation while allowing relative displacement therebetween in at least one direction.
In another form of the present invention, a diffuser for a gas turbine includes a diffuser having an inner wall spaced from an outer wall to define an annular flowpath, and a plurality of struts coupled between the inner and outer walls to maintain the inner and outer walls in spaced relation while allowing the inner and outer walls to float relative to one another in a radial direction.
In a further form, a diffuser for a gas turbine engine is provided, including first and second flowpath structures, a strut coupled to the first and second flowpath structures to maintain the structures in spaced relation to define a flowpath, and a shroud member extending into the flowpath and positioned adjacent the strut to shield at least a portion of the strut from fluid flowing through the flowpath.
In yet another form, a diffuser for a gas turbine engine is provided, including an inner wall, an outer wall spaced from the inner wall to define a flowpath, and means for transmitting loads between the inner and outer walls while allowing substantially unrestrained relative movement therebetween in at least one direction.
One object of the present invention is to provide a unique diffuser for a gas turbine engine.
Further forms, embodiments, objects, features and aspects of the present invention shall become apparent from the drawings and descriptions provided herein.